High Resolution Measurements and Electronic Structure Calculations of a Diazanaphthalene: [1,6]-naphthyridine. Sébastien Gruet, Manuel Goubet, Olivier Pirali ISMS /06/2014

2 Structure of small PAHs molecules Complementarity of MW and IR data Principal sources of rotational informations (GS) – Microwave spectroscopy – UV for centrosymmetric molecules Y. Semba et al. J. Chem. Phys. 131, (2009) Publications of high resolution IR data are scarce S. Albert et al. Faraday Discuss. 150, (2011) B. E. Brumfield et al. J. Phys. Chem. Lett. 3, (2012) O. Pirali et al. PCCP, 15, (2013) Rotational resolved data in the Literature Hypothesis A. Leger, J. L. Puget, A&A 1984, 137, L5. Peeters et al, 2002, A&A,390, 1089

Mid- & Near Infrared (Classical Sources) Mid- & Near Infrared (Classical Sources) 3 (372) 3000 (372) (62) 500 (62) 500 (12) 100 (12) 100 (1.2) 10 (1.2) Far-Infrared The AILES Beamline (Synchrotron Radiation) Far-Infrared The AILES Beamline (Synchrotron Radiation) Fundamental vibrational modes of PAHs (meV) cm -1 Room temperature long pathlength cell Optical pathlength : 150 m Spectral range : 30 – 1000 cm -1 Resolution : cm -1 ≈ 30 MHz Spherical moving mirror MW Radiation Gas injection L-shaped antenna Vacuum : ≈ mbar Step by step motor Stainless steel cell Spherical mirror (Aluminum) Pumping group Pulsed nozzle Gaussian beam profile W 0 = 42 mm à 12 GHz 1200 mm Supersonic Jet Set-up of the FT-MW spectrometer Spectral range : 4 – 20 GHz ≈ 0.13 – 0.67 cm -1 Resolution : 1.8 kHz ≈ cm -1 MicroWave The PhLAM Laboratory (Electronic sources) MicroWave The PhLAM Laboratory (Electronic sources) Pure Rotational Transitions of PAHs (0.06) 0.5 (0.06) 0.5

4 Pure Rotational Spectrum PhLAM Laboratory Pure Rotational Spectrum PhLAM Laboratory Ro-vibrational Spectrum AILES Beamline Ro-vibrational Spectrum AILES Beamline

c b 5 Infared transitions Out of plane vibrational modes c a b μ a = 1.55 D μ b = 0.46 D Microwave transitions a-type b-type + hyperfine structure c-type

Collaboration with M. Goubet from the PhLAM laboratory at Lille 6 Spherical moving mirror MW Radiation Gas injection L-shaped antenna Vacuum : ≈ mbar Step by step motor Stainless steel cell Spherical mirror (Aluminum) Pumping group Pulsed nozzle Gaussian beam profile W 0 = 42 mm à 12 GHz 1200 mm Supersonic Jet

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8 [1,6]-naphthyridine Par. GS (Combined fit: MW + IR data) ν 38 ν 34 Band Center MHz/cm (45) / (15) (47) / (16) A (70) (68) (54) B (30) (40) (73) C (21) (57) (12) Δ J (11) (12) c Δ K (89) (96) c Δ JK (58) (66) c δ J (61)5.598 c δ K (16)70.4 c χ aa (N1)1.5191(18) χ bb (N1) (12) χ aa (N6) (15) χ bb (N6)0.2234(17) N lines MW/IR RMS MHz cm -1 J” Ka”Ka”

9 Anharmonic DFT calculation at the B97-1/cc-pVTZ//ANO-DZP level Accurate calculated rotational parameters More details about calculations: M. Goubet, O. Pirali, J. Chem Phys. 140, (2014) Useful tool to begin the GSCD analysis by LWW diagram [1,6]-naphthyridine ModeGS ParametersCalculatedExperimentalDeviationCalculatedExperimentalDeviationCalculatedExperimentalDeviation A /MHz B /MHz C /MHz Anharmonic DFT calculation at the B97-1/cc-pVTZ//ANO-DZP level Corrected Calculated Values ExperimentalDeviation Corrected Calculated Values ExperimentalDeviation

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Combining MW and FT-FIR data: – Excited states of small PAHs and derivatives FA09 – Roger Adams Lab 116 – 11 h 01 to 11 h 16 AM – Spectroscopy of diamond-like and biphenyl-like molecules 11 Important database of rotational information in the IR  Simulation at different resolution and at low temperature Pure carbonated PAHs PANHs (PAHs with nitrogen atoms)